FM translators for AM

In general
AM Revitalization
FM translators for AM stations attempt to provide the AM daytime coverage 24 hours a day via 250 watt or less transmissions in the FM broadcast band.
Having an FM signal can be a boon for station advertising revenue–provided the FM coverage is not disrupted by unexpected factors such as illegal “pirate” broadcasters.
The Feb. 2017 R&O extended the 60 dBu (1 mV/m) FM translator contour to the greater of the AM 2 mV/m contour or 25 mile radius.

WROL W262CV 100.3 specifications

WROL FM translator interference

The 100.3 pirates moved to 105.3, but WROL 100.3 faces severe challenges from,
and presents new challenges to other licensed stations.
Listeners to these existing stations may object to the new WROL 100.3 translator.

Pirates vs. FM translator

Pirate broadcasting is cheap and effective.
$500 of equipment & antenna on top of a church or apartment building provides 3-5 miles of coverage radius.
This has led to widespread pirate broadcasts in urban areas to service ethnic/language niche markets not economically served 24 hours a day by other means.

The Blue Hill Ave pirates have a cluster of three antennas for 87.75, 105.3 and formerly 100.3 MHz.
The interference-free coverage and transmitter quality of 87.75 and 105.3 is nearly the same.
Transmitter power appears to be in the 10-100 watt range.

Cochannel

50 kW WHEB is the primary limitation to coverage, particularly in the northeastern parts of Boston.
However, one can merely switch to WROL 950 AM in northeast exurbs of Boston.